Added a shader clearing call in ScreenMesh rendering, fixed zlib URL

CMake/ExternalPNG.cmake

@@ -17,8 +17,8 @@ EXTERNALPROJECT_ADD(zlib
     PREFIX ${libpng_PREFIX}
 
     DOWNLOAD_DIR ${POLYCODE_DEPS_DOWNLOAD_DIR}
-    URL http://zlib.net/zlib-1.2.7.tar.gz
-    URL_MD5 60df6a37c56e7c1366cca812414f7b85
+    URL http://zlib.net/zlib-1.2.8.tar.gz
+    URL_MD5 44d667c142d7cda120332623eab69f40
 
     PATCH_COMMAND ${CMAKE_COMMAND} -E copy_if_different ${PolycodeDependencies_SOURCE_DIR}/../CMake/zlib.cmake <SOURCE_DIR>/CMakeLists.txt && ${CMAKE_COMMAND} -E remove <SOURCE_DIR>/zconf.h
 

Core/Contents/Source/PolyScreenMesh.cpp

@@ -132,6 +132,8 @@ void ScreenMesh::setMaterialByName(const String& materialName) {
 void ScreenMesh::Render() {	
 	Renderer *renderer = CoreServices::getInstance()->getRenderer();
 	
+	renderer->clearShader();
+	
 	renderer->setLineSize(lineWidth);
 	renderer->setLineSmooth(lineSmooth);